1. Field of the Invention
The invention relates to a spool assembly designed to have a wire encapsulated thereabout. More particularly, the invention relates to a spool assembly having a flow channel allowing for the efficient replacement of air with an insulating material into the wire wound thereabout.
2. Description of the Related Art
Transformers, such as ignition coils, have primary and secondary windings of electrical wire wound about a spool. In the case of an ignition coil, the secondary coil is a high voltage coil and must contain no air. Air is removed from the secondary coil by forcing an insulating material into the secondary winding. A current method of forcing the insulating material into the winding is the casting of liquid into the winding after first lowering the encapsulation chamber atmosphere to around 1 mBar. The most efficient impregnation techniques using the above-mentioned method will yield a residual air volume of approximately 0.1%, depending upon the ambient air pressure. In the current designs, the only direction that the liquid insulator can flow into the secondary winding is through the very fine and tightly wound wire. One of the effects of having the liquid insulator travel through the secondary winding is that small pockets of residual air will have a tendency to be located on the interface between the spool and the inside diameter of the winding (typically in the thickest sections of the wound wire).
Referring to FIG. 1, a cross section of a prior art spool assembly is generally indicated at 10. A spool assembly 10 includes a cylinder 12 having an electrical winding 14 wound about the cylinder 12 of the spool assembly 10. An air void 16 can exist between the electrical winding 14 and the cylinder 12 where the electrical winding 14 is the thickest. The air void 16 reduces the reliability of the spool assembly 10.